JP7707096B2 - Sound pressure detector - Google Patents

Description

The present invention relates to a sound pressure detection device.

Conventionally, a sound pressure detection device is known that includes a device housing, a cover, a vent, a substrate, and a sound pressure sensor (see, for example, Patent Document 1). In the sound pressure detection device described in Patent Document 1, the substrate is fixed to the inner peripheral end surface of the opening of the device housing via a shield plate and an O-ring. The sound pressure sensor is attached in close contact with the substrate on an extension of the sound propagation path provided in the device housing so as to measure only the desired sound pressure and prevent a decrease in accuracy due to picking up ambient noise.

JP 2020-113874 A

However, in conventional sound pressure detection devices, a shield plate is placed in close contact with the substrate to prevent the intrusion of electromagnetic noise from the external environment, and this shield plate abuts against an O-ring to support the pressing force. However, if the shield plate is omitted in an environment where there is no or only little influence of electromagnetic noise, the substrate will be subjected to pressing force from the O-ring, and the substrate will deform, which may reduce the detection accuracy and output accuracy from the sound pressure sensor. In addition, due to differences in the linear expansion coefficients of the substrate, shield plate, and device housing, a change in ambient temperature could also cause the substrate to deform, potentially reducing the detection and output accuracy.

The present invention aims to obtain a sound pressure detection device that has a substrate structure that is resistant to deformation due to pressure or temperature changes, thereby suppressing deterioration in the accuracy of sound pressure detection and the accuracy of output from the sound pressure sensor.

In order to solve the above problems, the sound pressure detection device of the present invention is a sound pressure detection device that includes a device housing, a sound propagation path that communicates with the inside and outside of the device housing and propagates sound from the outside, a substrate provided at the inside end of the sound propagation path of the device housing, a sound pressure sensor provided on the substrate, and a cover that closes the opening of the device housing to form an internal space of the housing, and is characterized in that the device housing is provided with at least a pair of spaced fixing parts that fix the substrate, and the distance between one of the fixing parts and the other fixing part is 11.0 times or less the plate thickness dimension of the substrate.

According to the present invention, the distance between the pair of fixing parts is set to 11.0 times or less the thickness dimension of the substrate, so that the thickness of the substrate is relatively thicker than the distance between the fixing parts, and the rigidity of the substrate can be improved. Therefore, deformation of the substrate can be suppressed compared to a conventional configuration in which the substrate receives a pressing force from an O-ring when the shield plate is omitted. In addition, by making the thickness of the substrate relatively thicker than the distance between the fixing parts, deformation of the substrate due to the difference in the linear expansion coefficient between the substrate and the device housing when the ambient temperature changes can be suppressed. Therefore, by having a substrate structure that is less likely to deform due to pressing forces or temperature changes, a sound pressure detection device can be obtained that can suppress deterioration in the detection accuracy of sound pressure and the output accuracy from the sound pressure sensor.

In this case, it is preferable that the substrate is attached to the end of the sound propagation path on the inside side of the device housing via an annular elastic member that abuts the substrate in the thickness direction. With this configuration, the substrate can be attached to the device housing via an annular elastic member that abuts the substrate in the thickness direction, which prevents gaps from occurring at the attachment portion due to close contact between the substrate and the device housing, suppresses sound leakage from the sound propagation path from that portion, and suppresses a decrease in sensor output. Furthermore, since the pressing force when attaching the substrate to the device housing can be absorbed by the elastic member, the pressing force generated on the substrate can be reduced and deformation of the substrate can be suppressed compared to a configuration that does not use an elastic member.

It is also preferable that the device housing is provided with a convex portion having a width dimension smaller than the width dimension of the elastic member, and that the convex portion abuts against a widthwise intermediate portion of the elastic member. According to this configuration, by having the convex portion having a width dimension smaller than the width dimension of the elastic member abut against a widthwise intermediate portion of the elastic member, the contact area between the device housing and the elastic member can be reduced compared to a configuration in which a convex portion is not provided. This makes it possible to reduce the range in which a reaction force is generated when the elastic member is pressed by the device housing, thereby reducing the effect of the reaction force on the substrate and suppressing deformation of the substrate.

In addition, at the end of the sound propagation path on the inside of the device housing, a substrate mounting section on which the substrate is mounted with the substrate's thickness direction as the mounting direction, and a mounting section which is recessed in the mounting direction and in which the elastic member is installed in the mounting direction are formed, and the mounting section is provided with a convex portion which protrudes toward the substrate mounting section in the mounting direction within an area not exceeding the substrate mounting section, and the convex portion has a width dimension smaller than the width dimension of the elastic member and is installed so as to abut against the surface of the elastic member on one side in the mounting direction over its entire circumference, and it is preferable that the dimension in the mounting direction from the substrate mounting section to the top of the convex portion is set to be equal to or smaller than the dimension in the mounting direction of the elastic member installed in the mounting section. According to this configuration, the dimension in the placement direction from the substrate placement portion to the top of the convex portion is set to be equal to or less than the dimension in the placement direction of the elastic member, i.e., equal to or less than the thickness of the elastic member. Therefore, when the elastic member is attached, the surface of the elastic member opposite the surface that abuts against the convex portion protrudes in the placement direction from the substrate placement portion or is flush with the substrate placement portion, so that the substrate can always compress the elastic member or abut against the elastic member. Furthermore, by setting the dimension in the placement direction from the substrate placement portion to the top of the convex portion to be equal to or less than the thickness of the elastic member, the substrate can be fixed with a constant amount of compression of the elastic member regardless of the mounting state. Furthermore, since an apparent groove is formed in the mounting portion, even if the elastic member is deformed by being pressed against the convex portion, a part of the deformed elastic member can escape into the groove.

In addition, it is preferable that the elastic member is provided inside the device housing between the periphery of the opening of the sound propagation path on the inside side of the device housing and the substrate, and the fixing portion is provided near the radial outside of the tip of the opening of the sound propagation path on the inside side of the device housing. According to this configuration, since the fixing portion is provided near the radial outside of the tip of the opening of the sound propagation path on the inside side of the device housing, each fixing portion can be brought as close as possible to the center side of the substrate, and the separation distance between the pair of fixing portions can be reduced. This allows the plate thickness dimension of the substrate to be relatively large with respect to the separation distance, and the rigidity of the substrate can be improved. In addition, the plate thickness of the substrate to satisfy the relationship between the above-mentioned separation distance and the plate thickness dimension of the substrate can be made thinner compared to a configuration in which the separation distance is large, and the sound pressure detection device can be prevented from becoming large.

The substrate is preferably provided to close the tip of the sound propagation path at the opening on the inside of the device housing, and the substrate is preferably provided with at least one minute air hole that connects the sound propagation path to the housing internal space. According to this configuration, the substrate that closes the tip of the sound propagation path at the opening on the inside of the device housing has a minute air hole that connects the sound propagation path to the housing internal space, so that the air pressure in the sound propagation path and the air pressure in the housing internal space become equal, and condensation can be prevented from occurring in the housing internal space.

According to the present invention, a sound pressure detection device can be obtained that has a substrate structure that is resistant to deformation due to pressure or temperature changes, and that can suppress deterioration in the accuracy of sound pressure detection and output from the sound pressure sensor.

1 is a cross-sectional view of a sound pressure detection device according to an embodiment of the present invention. 3A is a front view of a device housing of the sound pressure detection device, and FIG. 3B is a cross-sectional view taken along line AA of FIG. FIG. 2(A) is a cross-sectional view taken along line BB of FIG. 1A is a partial enlarged view of the sound pressure measuring device before the substrate is fixed, and FIG. 1B is a partial enlarged view of the sound pressure measuring device after the substrate is fixed. FIG. FIG. 4A is an exploded perspective view of the sound pressure detection device, and FIG. 4B is a perspective view of the sound pressure detection device from the rear side with a substrate attached to the device housing.

Embodiments of the present invention will now be described with reference to Figs. 1 to 6. Fig. 1 is a cross-sectional view of a sound pressure detection device 100 according to one embodiment of the present invention. Fig. 2(A) is a front view of the device housing 10 of the sound pressure detection device 100, and Fig. 2(B) is a cross-sectional view taken along line A-A in Fig. 2(A). Fig. 3 is a cross-sectional view taken along line B-B in Fig. 2(A).

In the drawings, the arrows X, Y, and Z are mutually orthogonal directions. In this embodiment, the direction from one side of the device housing 10 to the other side is indicated by the arrow X, and the arrow X is referred to as the "left-right direction X". The left side of the left-right direction X is referred to as the "left side X1", and the right side is referred to as the "right side X2". The direction orthogonal to the left-right direction X of the device housing 10 is indicated by the arrow Y, and the arrow Y is referred to as the "front-rear direction Y". The front side of the front-rear direction Y is referred to as the "front side Y1", and the rear side is referred to as the "rear side Y2". The direction perpendicular to the left-right direction X and the front-rear direction Y is indicated by the arrow Z, and is referred to as the "upper-lower direction Z". The upper side of the up-down direction Z is referred to as the "upper side Z1", and the lower side is referred to as the "lower side Z2".

The sound pressure detection device 100 according to this embodiment is disposed near a sound source (e.g., a speaker, etc.) and is used to detect whether the sound source is functioning normally. The sound pressure detection device 100 is used, for example, to detect warning sounds at railroad crossings and guidance sounds at pedestrian crossings. As shown in FIG. 1, the sound pressure detection device 100 includes a box-shaped device housing 10, a sound propagation path 20 that propagates sound from the outside, a vent portion 30 provided on the outside side of the sound propagation path 20, a substrate 40 provided on the inside side of the sound propagation path 20, a sound pressure sensor 50 provided on the substrate 40, an elastic member 60 that abuts against the substrate 40 in the plate thickness direction, and a cover 70 that closes an opening provided in the device housing 10 to form a housing internal space 10c1.

The device housing 10 houses each component constituting the sound pressure detection device 100 to ensure waterproofing and protection from the external environment. As shown in FIG. 2, a female screw 10a, a groove 10b, and an opening 10c are formed on the wall of the rear side Y2 of the device housing 10. The female screw 10a is a portion into which the bolt 11 is tightened when fixing the cover 70 to the device housing 10, and is formed at the four corners of the wall of the rear side Y2 of the device housing 10. The groove 10b is a groove for arranging a seal member 12 such as an O-ring, and is formed in a circular shape when viewed from the rear of the device housing 10. The opening 10c is formed in a substantially circular shape along the inner edge of the groove 10b at a portion inside the inner edge of the groove 10b, and is open so as to communicate with the inside and outside of the device housing 10. This opening 10c is closed by the cover 70 described later, and when closed by the cover 70, a housing internal space 10c1 is formed inside the opening 10c. As shown in FIG. 1, an outlet 10d that opens in the vertical direction Z is formed in the wall of the lower side Z2 of the device housing 10, and a cable 13 for outputting a sound pressure signal is attached to this outlet 10d via a mounting member 13a.

A cylindrical wall portion 14 is formed on the wall portion of the front side Y1 of the device housing 10, rising to the rear side Y2 and penetrating in the front-rear direction Y. A substrate placement portion 17 for placing a substrate 40 in the front-rear direction Y (plate thickness direction, placement direction) is formed on the end portion of the rear side Y2 of the cylindrical wall portion 14 (end portion on the inside side of the device housing 10). Also, a mounting portion 15 for placing an elastic member 60 on the front side Y1 side (placement direction) of the substrate placement portion 17 is formed on the inner peripheral side of the substrate placement portion 17 at the end portion of the rear side Y2 of the cylindrical wall portion 14. As shown in FIG. 2 (A), the mounting portion 15 is formed in a circular shape when viewed from the rear of the device housing 10. The inner diameter dimension of the mounting portion 15 is set smaller than the outer diameter dimension of the elastic member 60 so that the elastic member 60 described later does not fall off. Also, the outer dimension of the mounting portion 15 is set larger than the outer diameter dimension of the elastic member 60 so that the elastic member 60 does not ride up.

The mounting portion 15 has a step recessed from the substrate placement portion 17 toward the front side Y1. That is, the mounting portion 15 is recessed toward the front side Y1 (placement direction). The mounting portion 15 has a protrusion 15a on the rear side Y2 (substrate placement portion 17 side in the placement direction) that protrudes within a range not exceeding the substrate placement portion 17. For this reason, the periphery of the protrusion 15a is relatively recessed toward the front side Y1, and this portion constitutes a recess 15b. As shown in FIG. 2A, the protrusion 15a and the recess 15b are formed in a circular shape when viewed from the rear of the device housing 10. As shown in FIG. 4A, the width dimension s1 of the protrusion 15a is set smaller than the width dimension s2 of the elastic member 60, and the top of the protrusion 15a is adapted to abut the entire periphery of the widthwise middle portion of the surface of the front side Y1 of the elastic member 60 (surface on one side in the placement direction). The recess 15b is a portion that allows a portion of the deformed elastic member 60 to escape when the elastic member 60 deforms, and its depth, i.e., the dimension from the top of the protrusion 15a to the bottom of the recess 15b, is set to be equal to or greater than the deformation allowance s4 of the elastic member 60 shown in Fig. 4(B). In addition, the dimension s3 from the board mounting portion 17 to the top of the protrusion 15a (also called the dimension in the mounting direction, height difference, or component dimension) is set to be equal to or less than the thickness t2 of the elastic member 60 (the dimension in the mounting direction of the elastic member 60 installed in the mounting portion 15).

2A, a pair of connecting plate portions 14a are formed at the end of the rear side Y2 of the cylindrical wall portion 14 (the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10), i.e., at both ends in the left-right direction X of the mounting portion 15, which extend in the left-right direction X and are connected to the wall portion of the rear side Y2 of the device housing 10. Each connecting plate portion 14a is formed with a fixing portion 16 for fixing the substrate 40 to the device housing 10. That is, the device housing 10 is provided with at least a pair of spaced fixing portions 16 for fixing the substrate 40. The fixing portion 16 is formed at a position near the cylindrical wall portion 14 on the plate surface of the rear side Y2 of the connecting plate portion 14a. That is, the fixing portion 16 is provided in the radially outer vicinity of the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10. This fixing portion 16 is configured with a female thread for tightening the screw 16a (see Figures 6 (A) and (B)) when fixing the substrate 40 to the device housing 10.

The amount of deformation of the substrate 40, the amount of deformation of the elastic member 60, and the reaction force due to excessive deformation of the elastic member 60 are influenced by the amount of tightening (i.e., tightening torque) when the substrate 40 is tightened to the fixing portion 16 with the screw 16a, the difference in the linear expansion coefficient of the device housing 10 and the substrate 40 due to temperature changes, etc., so it is preferable to adjust the pitch L (separation distance, see Figures 2 (A) and 5) between one fixing portion 16 and the other fixing portion 16 so that it is relatively small with respect to the plate thickness dimension t1 (see Figure 1) of the substrate 40. In other words, it is preferable to make the plate thickness dimension t1 in the front-rear direction Y of the substrate 40 relatively large with respect to the pitch L. In other words, the smaller the ratio L/t of the pitch L of the fixing portion 16 to the plate thickness dimension t1 of the substrate 40, the smaller the amount of deformation of the substrate 40 can be. Specifically, when L = 19 mm, the amount of deformation of the substrate 40 can be made smaller when t = 3.2 mm and the ratio L/t is 5.9 than when t = 1.6 mm and the ratio L/t is 11.8. Therefore, in this embodiment, the pitch L between one fixing part 16 and the other fixing part 16 is set to 11.0 times or less the plate thickness dimension t1 of the substrate 40, and preferably, to 8.0 times or less the plate thickness dimension t1.

In this embodiment, the fixing portion 16 is configured with a pair of female screws as described above, but in addition to the female screws, the fixing portion 16 may be configured to fix the device housing 10 and the substrate 40 by hooking with a claw extending from the device housing 10 side or the substrate 40 side, or the fixing portion 16 may be configured by hooking with a claw or by using a combination of a screw and a claw. Furthermore, adhesive may be applied to the end surface of the back side Y2 of the cylindrical wall portion 14 over the entire circumference of the opening, and the part to which the adhesive is applied may be the fixing portion 16, or the substrate 40 may be fixed to the device housing 10 by attaching an adhesive sheet, double-sided tape, or the like. In this embodiment, a pair of fixing portions 16 is provided, but one or more pairs of fixing portions 16 may be provided to support the substrate 40 at three points. In this embodiment, it is preferable that the substrate mounting portion 17, the fixing portion 16, and the connecting plate portion 14a are on the same plane. This configuration makes it possible to prevent undesirable stress from being applied to the substrate 40 when the substrate 40 is fixed, which would cause the substrate 40 to deform from its initial state.

1, the inner wall surface of the cylindrical wall portion 14 is formed with a female thread 14b that screws into a male thread 31a formed on the outer wall surface of the vent body 31 of the vent portion 30, which will be described later. The inside of the cylindrical wall portion 14 forms a linear space extending in the front-rear direction Y, and this space constitutes a sound propagation path 20 that communicates with the inside and outside of the device housing 10 and propagates sound from the outside. That is, the cylindrical wall portion 14 surrounds the periphery of the sound propagation path 20. The tip of the rear side Y2 of the cylindrical wall portion 14 constitutes the tip of the opening of the sound propagation path on the inside side of the device housing 10. In this embodiment, the cylindrical wall portion 14 surrounds the periphery of the sound propagation path 20, but for example, it is also possible to make the wall portion of the front side Y1 of the device housing 10 thick and form a through hole penetrating the thick wall portion in the front-rear direction Y, and use the through hole as the sound propagation path 20, and omit the cylindrical wall portion 14. In this case, the above-mentioned substrate placement portion 17 and mounting portion 15 are formed at the end of the rear side Y2 of the thick wall portion, and a fixing portion 16 is provided near the radially outer side of the tip of the sound propagation path 20 at the opening on the inside side of the device housing 10.

The vent section 30 is provided on the front side Y1 (outside the device housing 10) of the sound propagation path 20. The vent section 30 is a member that covers the sound propagation path 20, and is waterproof, dustproof, and breathable. The vent section 30 includes a cylindrical vent body 31 and a columnar cap section 32 that protrudes radially outward from the end of the front side Y1 of the vent body 31. A male thread 31a is formed on the outer circumferential surface of the vent body 31. The inside of the vent body 31 constitutes the sound propagation path 20 in the same manner as the cylindrical wall section 14 of the device housing 10.

The cap portion 32 has a plurality of first through holes 32a formed in the circumferential direction, each penetrating radially toward the center and communicating with the inside and outside, and a second through hole 32b formed in the center, communicating each of the first through holes 32a with the space inside the vent body 31, and penetrating in the front-rear direction Y. When attaching the vent portion 30 to the device housing 10, the male screw 31a is fastened to the female screw 14b on the inside of the cylindrical wall portion 14 with a sealing retaining ring 33 attached to the end of the front side Y1 of the outer peripheral wall of the vent body 31, thereby fixing the vent portion 30 to the device housing 10.

The substrate 40 is attached to the substrate placement portion 17 via an annular elastic member 60 that contacts the substrate 40 in the front-rear direction Y (thickness direction), and is provided to close the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10. As shown in FIG. 5, the substrate 40 is formed in an octagonal plate shape when viewed from the front. The substrate 40 is a printed circuit board on which a sound pressure sensor 50 for detecting sound pressure and an IC chip (not shown) for reading signals are mounted. At the center of the substrate 40, a through hole 40a that communicates with the sound propagation path 20 and passes sound waves is formed in the front-rear direction Y (thickness direction). At least one or more minute ventilation holes 40b that communicate the sound propagation path 20 and the housing internal space 10c1 are provided on the upper side Z1 of the through hole 40a. The ventilation hole 40b is a hole for equalizing the pressure between the sound propagation path 20 and the housing internal space 10c1, and has a humidity control function. The diameter of a through hole in a typical electronic circuit board is set to 0.8 to 1.0 mm to correspond to the diameter of the lead wires of electronic components. In this embodiment, however, with a typical hole diameter, the sound pressure sensor 50 cannot pick up all the sound propagating through the sound propagation path 20, lowering the sensor output and resulting in an error, so the hole diameter of the ventilation hole 40b is set to approximately 0.3 mm.

A connector section 41 is provided on the upper side Z1 of the substrate 40, and the signal line 13b of the cable 13 is connected to the connector section 41. A pair of screw holes 40c are formed at both ends of the substrate 40 in the left-right direction X, penetrating the substrate 40 in the front-rear direction Y (plate thickness direction). The screw holes 40c are holes through which the screws 16a are passed to be fastened to the fixing section 16. When the substrate 40 is attached to the device housing 10, the substrate 40 is arranged so that the central axis of the screw holes 40c is coaxial with the central axis of the fixing section 16, as shown in FIG. 6(A) and FIG. 6(B), and the substrate 40 is fastened and fixed by the screws 16a. The sound pressure sensor 50 is arranged on the plate surface (mounting surface) on the rear side Y2 of the substrate 40 so as to close the end of the rear side Y2 of the through hole 40a. For example, a capacitive MEMS acoustic sensor chip is used for the sound pressure sensor 50. A MEMS acoustic sensor chip is a small acoustic sensor formed on a semiconductor substrate using MEMS (micro electro-mechanical system) technology.

The elastic member 60 is a member interposed between the substrate 40 and the mounting portion 15 when the substrate 40 is attached to the device housing 10, and is formed in a circular (annular) shape in a plan view using butyl rubber with a deformation allowance s4 in the front-rear direction Y so as to absorb the pressing force in the front-rear direction Y (plate thickness direction) against the substrate 40. The width dimension s2 of the elastic member 60 is set to be larger than the dimension in the front-rear direction Y, and thus the cross-sectional shape is formed in a rectangular flat plate shape as shown in FIG. 4 (A). As shown in FIGS. 4 (A) and (B), this elastic member 60 is arranged between the periphery of the opening on the back side Y2 (inside the device housing 10) of the sound propagation path 20 and the substrate 40. When the substrate 40 is attached to the mounting portion 15, the elastic member 60 is pressed toward the front side Y1 and deformed. At this time, the elastic member 60 is arranged to close the gap between the mounting portion 15 and the substrate 40. In other words, the elastic member 60 is arranged to close the inside of the sound propagation path 20. In this manner, when the substrate 40 is placed in contact with the substrate placement portion 17, the dimension s3 from the substrate placement portion 17 to the top of the protrusion 15a is set, so that the substrate 40 can be fixed so that the amount of compression of the elastic member 60 is constant. This configuration prevents sound leakage from the sound propagation path 20 to the housing internal space 10c1, preventing a decrease in sensor output due to input attenuation to the sound pressure sensor 50 caused by the sound leakage, and preventing output errors of the sound pressure sensor due to sound diffraction caused by the sound leakage.

The elastic member 60 is not limited to butyl rubber, and may be made of silicon packing, high-density urethane foam, or the like. In the present embodiment, the elastic member 60 is fixed to the device housing 10 in a state where it is sandwiched between the mounting portion 15 and the substrate 40. However, the elastic member 60 may be fixed to the device housing 10 by, for example, applying an adhesive to one side of the elastic member 60, or by attaching an adhesive sheet or double-sided tape. The elastic member 60 may be made of a so-called flat packing having a flat circular plate shape as in the present embodiment, or may be made of a caulking material such as silicone. The elastic member 60 is made to have a circular (annular) shape in a plan view, but this is not limited to a circular shape in a plan view as long as it has a shape based on the planar shape of the rear side Y2 opening of the sound propagation path 20. In other words, if the shape is such that it can abut against the end of the rear side Y2 opening of the sound propagation path 20 around the entire circumference, and also abuts against the substrate 40, and seals the rear side Y2 opening of the sound propagation path 20 around the entire circumference, it is possible to maintain the effect of preventing sound leakage from the sound propagation path 20.

The elastic member 60 may have a circular cross-sectional shape instead of a flat plate shape as in this embodiment. When the elastic member 60 has a flat cross-sectional shape, the contact area between the elastic member 60 and the substrate 40 can be increased, so that the reaction force when the substrate 40 is pressed against the front side Y1 can be increased, and the substrate 40 can be stably maintained in contact with the elastic member 60. On the other hand, when the elastic member 60 has a circular cross-sectional shape, the contact area between the elastic member 60 and the substrate 40 can be reduced, so that the reaction force when the substrate 40 is pressed against the front side Y1 can be reduced, and the risk of deformation of the substrate 40 can be reduced.

The cover 70 is a lid member that closes the opening 10c of the device housing 10. The cover 70 is a plate-shaped member with an outer edge that follows the outer edge of the opening 10c of the device housing 10. When the cover 70 is fixed to the device housing 10, the opening 10c is closed and an internal space 10c1 of the housing is formed on the back side Y2 of the substrate 40 (the side opposite to the sound propagation path 20). The cover 70 is not limited to a plate-shaped member, and may be, for example, a screw-type lid that can be screwed to the opening 10c like the vent portion 30 described above. The cover 70 may also have a cylindrical portion that is inserted into the opening 10c and engaged with an engagement claw, and a flange portion that protrudes to the back side Y2, and the flange portion may be sealed with the seal member 12.

The sound pressure detection device 100 according to this embodiment is assembled in the following procedure. First, as shown in FIG. 1, with the retaining ring 33 attached to the vent portion 30, the male screw 31a is fastened to the female screw 14b of the cylindrical wall portion 14 to attach the vent portion 30 to the device housing 10. Also, the cable 13 is attached to the outlet 10d of the device housing 10 via the mounting member 13a. Next, as shown in FIG. 6(A), the elastic member 60 is placed on the rear side Y2 of the device housing 10, and as shown in FIG. 1, the surface of the front side Y1 of the elastic member 60 is brought close to the surface of the rear side Y2 of the convex portion 15a of the mounting portion 15 and abutted against the surface. At this time, the top of the convex portion 15a is made to abut against the center of the width of the elastic member 60. Next, the substrate 40 is placed on the rear side Y2 of the device housing 10, and as shown in FIG. 1, the surface of the front side Y1 of the substrate 40 is brought close to the surface of the rear side Y2 of the elastic member 60 and abutted against the surface. Then, the central axis of the screw-through hole 40c of the substrate 40 and the central axis of the fixing portion 16 are aligned coaxially, and the screw 16a is fastened to the fixing portion 16 to fix the substrate 40 to the device housing 10. At this time, as shown in FIG. 4B, the front side Y1 surface of the substrate 40 abuts against the surface of the substrate mounting portion 17 and abuts against the rear side Y2 surface of the elastic member 60, pressing the elastic member 60 toward the front side Y1. The elastic member 60 is crushed and deformed by being pressed by the substrate 40. Then, when the substrate 40 is fixed to the device housing 10 in this manner, the elastic member 60 closes the gap between the mounting portion 15 and the substrate 40.

In this embodiment, when the substrate 40 is fixed to the device housing 10, the elastic member 60 is crushed to make the front side Y1 of the substrate 40 abut against the rear side Y2 of the substrate mounting portion 17. However, the front side Y1 of the substrate 40 does not have to abut against the rear side Y2 of the substrate mounting portion 17. That is, as long as the front side Y1 of the substrate 40 is in close contact with the elastic member 60, a gap may be generated between the substrate 40 and the substrate mounting portion 17. For this reason, the elastic member 60 does not necessarily have to be deformed, and even if the deformation allowance s4 of the elastic member 60 is 0, that is, in a state in which the substrate 40 is in abutment against the mounting portion 15 and the substrate 40 without being compressed, a gap may be generated between the substrate 40 and the substrate mounting portion 17. Therefore, when designing, the height of the convex portion 15a or the thickness of the elastic member 60 may be adjusted, or the amount of tightening of the screw 16a may be adjusted, so that no gap is generated between the elastic member 60 and the substrate 40. Then, after the board 40 is fixed to the device housing 10, the signal line 13b is connected to the connector portion 41 of the board 40, and then the opening 10c is closed with the cover 70. In this way, the sound pressure detection device 100 is completed.

According to this embodiment, the sound pressure detection device 100 includes a device housing 10, a sound propagation path 20 that communicates with the inside and outside of the device housing 10 and propagates sound from the outside, a substrate 40 provided on the back side Y2 (the end on the inside side of the device housing 10) of the sound propagation path 20, a sound pressure sensor 50 provided on the substrate 40, and a cover 70 that closes the opening of the device housing 10 to form the housing internal space 10c1. The device housing 10 is provided with at least a pair of spaced fixing parts 16 that fix the substrate 40, and the pitch L (separation distance) between one fixing part 16 and the other fixing part 16 is 11.0 times or less the plate thickness dimension t1 of the substrate 40.

According to the present invention, the pitch L between the pair of fixing parts is set to 11.0 times or less the thickness dimension t1 of the substrate 40, so that the thickness of the substrate 40 is made thicker relative to the pitch L of the fixing parts 16, and the rigidity of the substrate 40 can be improved. Therefore, deformation of the substrate 40 can be suppressed compared to a conventional configuration in which the substrate 40 receives a pressing force from an O-ring when the shield plate is omitted. In addition, by making the thickness of the substrate 40 thicker relative to the pitch L of the fixing parts 16, deformation of the substrate 40 due to the difference in the linear expansion coefficient between the substrate 40 and the device housing 10 when the ambient temperature changes can be suppressed. Therefore, by having a substrate 40 structure that is difficult to deform due to pressing forces and temperature changes, a sound pressure detection device 100 can be obtained that can suppress a decrease in the detection accuracy of sound pressure and the output accuracy from the sound pressure sensor 50.

In addition, in this embodiment, the substrate 40 is attached to the device housing 10 via an annular elastic member 60 that abuts the substrate 40 in the front-rear direction Y. Therefore, the substrate 40 can be attached to the device housing 10 via the annular elastic member 60 that abuts the substrate 40 in the plate thickness direction, which prevents gaps from occurring at the attachment portion due to close contact between the substrate 40 and the device housing 10, suppresses sound leakage from the sound propagation path 20 from that portion, and suppresses a decrease in the sensor output. Furthermore, since the pressing force when the substrate 40 is attached to the device housing 10 can be absorbed by the elastic member 60, the pressing force generated on the substrate 40 can be reduced and deformation of the substrate 40 can be suppressed compared to a configuration that does not use the elastic member 60.

In addition, by making the protrusion 15a, which has a width dimension s1 smaller than the width dimension s2 of the elastic member 60, contact the middle part of the elastic member 60 in the width direction, the contact area between the device housing 10 and the elastic member 60 can be made smaller than in a configuration in which the protrusion 15a is not provided. This makes it possible to reduce the range in which a reaction force is generated when the elastic member 60 is pressed by the device housing 10, thereby reducing the effect of the reaction force on the substrate 40 and suppressing deformation of the substrate 40.

In addition, since the dimension s3 from the board mounting portion 17 to the top of the convex portion 15a is set to be equal to or less than the thickness t2 of the elastic member 60, the compression amount of the elastic member 60 pressed against the convex portion 15a is determined by the dimension s3 (component dimension) from the board mounting portion 17 to the top of the convex portion 15a, so a constant compression amount can be ensured regardless of the mounting state. At this time, a recess 15b adjacent to the convex portion 15a is formed, so that a part of the pressed elastic member 60 can escape to the recess 15b. Therefore, the effect on the board 40 of the reaction force when the elastic member 60 is pressed from the device housing 10 can be reduced. Therefore, deformation of the board 40 due to the reaction force when the elastic member 60 is pressed from the device housing 10 can be suppressed.

In addition, by providing the fixing parts 16 near the radially outer side of the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10, each fixing part 16 can be brought as close as possible to the center of the substrate 40, and the pitch L of the pair of fixing parts 16 can be made small. This allows the plate thickness dimension t1 of the substrate 40 to be relatively large with respect to the pitch L, and the rigidity of the substrate 40 can be improved. In addition, the plate thickness of the substrate 40 to satisfy the relationship between the above-mentioned pitch L and the plate thickness dimension t1 of the substrate 40 can be made thinner compared to a configuration in which the pitch L is large, and the sound pressure detection device 100 can be prevented from becoming large.

In addition, the substrate 40 that closes the tip of the opening of the sound propagation path 20 on the inside side of the device housing 10 has a minute air vent 40b that connects the sound propagation path 20 to the housing internal space 10c1, so that the air pressure in the sound propagation path 20 and the air pressure in the housing internal space 10c1 are equal, preventing condensation from occurring in the housing internal space 10c1.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention includes design changes and the like within the scope of the present invention. In this embodiment, a pair of connecting plate parts 14a is formed at the end of the rear side Y2 of the cylindrical wall part 14, i.e., both ends of the mounting part 15 in the left-right direction X, and each connecting plate part 14a is formed with a fixing part 16 that is a female screw for fixing the board 40 to the device housing 10. However, the type and arrangement of the fixing part are not limited to this. For example, the end face of the rear side Y2 of the cylindrical wall part 14 and the surface of the front side Y1 of the board 40 may be bonded with an adhesive, and this adhesive part may be used as the fixing part.

In addition, the surface of the front side Y1 of the elastic member 60 may be bonded to the end of the back side Y2 of the cylindrical wall portion 14, and the surface of the back side Y2 of the elastic member 60 and the surface of the front side Y1 of the substrate 40 may be bonded with an adhesive, and this adhesive portion may be used as the fixing portion. In this case, the inner diameter dimension of the elastic member 60 is the separation dimension L (pitch L in this embodiment), but as described above, the outer dimension of the mounting portion 15 is set larger than the outer diameter dimension of the elastic member 60 so that the elastic member 60 does not ride up, so that the inner diameter dimension of the elastic member 60, i.e., the separation dimension L, can be made smaller than when the fixing portion 16 is formed on the connecting plate portion 14a extending in the left-right direction X of the mounting portion 15 as in this embodiment. Specifically, if the pitch L of the fixing portion 16 in this embodiment is L = 19 mm, the ratio L/t is 11.8 at t = 1.6 mm and 5.9 at t = 3.2 mm, whereas if the inner diameter dimension of the elastic member 60 is the separation dimension L, if L = 12 mm, the ratio L/t can be 7.5 at t = 1.6 mm and 3.7 at t = 3.2. Therefore, the plate thickness dimension t1 of the substrate 40 can be made even larger relative to the separation dimension L.

t1 Plate thickness dimension L Pitch (distance)
Reference Signs List 100 Sound pressure detection device 10 Device housing 16 Fixing portion 17 Substrate placement portion 20 Sound propagation path 30 Vent portion 40 Substrate 50 Sound pressure sensor 60 Elastic member 70 Cover

Claims (6)

A sound pressure detection device comprising: an apparatus housing; a sound propagation path that communicates between the inside and outside of the apparatus housing and propagates sound from the outside; a substrate provided at an end of the sound propagation path on the inside side of the apparatus housing; a sound pressure sensor provided on the substrate; and a cover that closes an opening of the apparatus housing to form an internal space of the housing,
A sound pressure detection device characterized in that the device housing is provided with at least a pair of spaced-apart fixing portions for fixing the substrate, and the distance between one of the fixing portions and the other of the fixing portions is 11.0 times or less the thickness dimension of the substrate. The sound pressure detection device according to claim 1, characterized in that the substrate is attached to the end of the sound propagation path on the inside side of the device housing via an annular elastic member that abuts against the substrate in the thickness direction. the device housing is provided with a protrusion having a width dimension smaller than a width dimension of the elastic member,
3. The sound pressure detection device according to claim 2, wherein the protrusion is in contact with a widthwise intermediate portion of the elastic member. a substrate placement section on which the substrate is placed with a thickness direction of the substrate as a placement direction, and a mounting section which is recessed in the placement direction and in which the elastic member is installed in the placement direction, are formed at an end of the sound propagation path on the inside side of the device housing;
the mounting portion is provided with a protrusion that protrudes toward the substrate placement portion in the placement direction within a range not exceeding the substrate placement portion,
the protrusion has a width dimension smaller than a width dimension of the elastic member and is provided so as to abut against a surface of the elastic member on one side in the placement direction over an entire periphery thereof,
3. The sound pressure detection device according to claim 2, wherein a dimension in the mounting direction from the substrate mounting portion to the top of the convex portion is set to be equal to or smaller than a dimension in the mounting direction of the elastic member installed in the mounting portion. the elastic member is provided inside the device housing between the substrate and a periphery of an opening of the sound propagation path on the inside side of the device housing,
5. The sound pressure detection device according to claim 2, wherein the fixing portion is provided in the vicinity of a radially outer side of a tip end of the opening of the sound propagation path on the inside side of the device housing. The sound pressure detection device according to any one of claims 1 to 5, characterized in that the substrate is provided to cover the tip of the opening of the sound propagation path on the inside side of the device housing, and the substrate is provided with at least one minute ventilation hole that connects the sound propagation path to the internal space of the housing.

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